POV-Ray : Newsgroups : povray.general : Specular, reflection and diffuse guidelines Server Time
25 Nov 2024 19:29:03 EST (-0500)
  Specular, reflection and diffuse guidelines (Message 1 to 2 of 2)  
From: FlyerX
Subject: Specular, reflection and diffuse guidelines
Date: 22 Mar 2013 16:38:15
Message: <514cc137$1@news.povray.org>
Hello,

Following the old lantern discussion on the images group I noticed that 
it was mentioned that, for more realistic results, R+D<1 to keep the 
reflected light intensity below the incoming light intensity. I also 
noticed that as a starting rule of thumb S<R with S=R/2 for most 
materials and S=R for metallic finishes.

How about specular highlight with relation to Diffuse? A very high 
specular value would show a reflected value higher than the incoming 
light. Should it be S+R+D<1?  Or is specular highlight independent? I am 
assuming only specular highlight (phong=0), albedo active, and 
conserve_energy is on.

Most likely I am wrong on this but I just wanted to know if this correct 
for more realistic materials.

FlyerX


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From: clipka
Subject: Re: Specular, reflection and diffuse guidelines
Date: 24 Mar 2013 21:22:05
Message: <514fa6bd$1@news.povray.org>
Am 22.03.2013 21:38, schrieb FlyerX:
> Hello,
>
> Following the old lantern discussion on the images group I noticed that
> it was mentioned that, for more realistic results, R+D<1 to keep the
> reflected light intensity below the incoming light intensity. I also
> noticed that as a starting rule of thumb S<R with S=R/2 for most
> materials and S=R for metallic finishes.
>
> How about specular highlight with relation to Diffuse? A very high
> specular value would show a reflected value higher than the incoming
> light. Should it be S+R+D<1?  Or is specular highlight independent? I am
> assuming only specular highlight (phong=0), albedo active, and
> conserve_energy is on.

Reflection and highlights both model the same surface property known as 
"specular reflection" by scientists. What POV-Ray calls "specular" 
actually models only specular reflection of light coming directly from 
light sources, while the "reflection" stuff models specular reflection 
of light coming via some other surfaces. Thus, ideally we would just 
have one brightness value governing both things.

Thus, for realistic results you should also have "S+D<1", but that's 
automatic if "R+D<1" and "S<=R".


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